This paper presents the design and implementation of a low-cost, general-purpose real-time simulation platform for a Modular Multilevel Converter - H-bridge (MMC-H) DC transformer, using a model design method. The approach mainly consists of two steps: a) establishing an equivalent mathematical model of the MMC-H topology, and on this basis, using the semiimplicit Euler method to derive the discretized updating model of the MMC-H state variables and b) using a hardware description language (HDL) coding tool to convert the fixed-point updating model into an equivalent HDL form. The above two-step method allows the flexible selection of Field Programmable Gate Array (FPGA) chips according to the circuit scale, and does not rely on manual HDL coding. The accuracy and performance of the realtime simulation platform are verified against matching MATLAB/Simulink simulation and experimental results. Finally, by comparing the hardware resource consumption of circuits of different scales on different FPGA computing platforms, the lowcost characteristics and versatility of the designed real-time simulation platform are verified.